Lysophosphatidic acid (LPA), a naturally occurring phospholipid, activates distinct members of the endothelial differentiation gene subfamily of G protein-coupled receptors to elicit multiple cellular responses. LPA was first implicated in ovarian cancer by the observation that LPA is present at elevated levels in ascites of ovarian cancer patients. LPA stimulates proliferation, survival, drug resistance and motility of ovarian cancer cells. However, the exact role of LPA in ovarian oncogenesis, particularly in vivo, remains poorly understood. We have recently performed cDNA microarrays to determine the profile of LPA-induced and repressed genes in ovarian cancer cells. One of the most striking changes induced by LPA was the dramatic induction of pro-angiogenic factors including interleukin 6 (IL-6), interleukin 8 (IL-8), growth-related oncogene a (GROa) and vascular endothelial growth factor (VEGF), suggesting that angiogenic factors are major target genes of LPA in ovarian cancer cells. These LPA-induced factors are important mediators of angiogenesis, tumorigenicity and cancer progression. In particular, high serum levels of IL-6 and IL-8 in ovarian cancer patients correlate with poor response to chemotherapy and poor prognosis. We hypothesize that LPA stimulation of angiogenic factor expression and neovascularization contributes to the pathogenesis of ovarian cancer. The hypothesis will be examined through 3 specific aims: A) To elucidate the mechanism by which LPA induces production of pro-angiogenic factors; B) To examine the role of LPA in the regulation of angiogenic factor expression in ovarian cancer cells; and C) To determine the role of LPA in neovascularization. LPA receptors and the intracellular signaling networks that link LPA to expression of angiogenic factors will be identified in ovarian cancer cells. We will then examine whether LPA is a primary endogenous regulator of angiogenic factor expression in ovarian cancer cells. The potential angiogenic activity of LPA will be studied by in vivo angiogenesis assay and in nude mouse xenograft models. These studies will improve our understanding of ovarian carcinogenesis and will potentially lead to a novel therapy targeting LPA receptors and LPA production. As a small phospholipid molecule, LPA signals through G protein-coupled receptors that are highly "drugable" molecules. More than half of all drugs in current use target this large family of cell surface receptors. [unreadable] [unreadable]